Territorial behavior among Western North American foragers: Allee effects, within group cooperation, and between group conflict
2019
Codding, Brian F. | Parker, Ashley K. | Jones, Terry L.
Ethnographic populations throughout Western North America relied on strategies and institutions to protect resources for exclusive use, though the degree of territorial defense varied significantly across the region. Attempts to explain this variation typically focus on the ecological contexts that promote economic defensibility, however, it is increasingly recognized that social dynamics also play a critical role because territoriality requires within group coordination or cooperation. Building on ideal distribution models, here we present a hypothesis for territorial defense that links ecological, economic, and social factors through Allee's principle: positive covariance between utility and the number of cohabiting individuals up to intermediate population densities. We predict that when foragers experience an Allee-like economy of scale, individual interests are more likely to align and facilitate within group cooperation and the exclusion of out-group competitors. We evaluate this model using data on 157 foraging populations from contact-era Western North America. The results support our predictions, showing that larger cooperative groups have greater levels of territorial behavior, specifically higher levels of resource ownership and intergroup violence. Thus, incorporating Allee's principles may help to explain how territorial behaviors can emerge, driven by the individual benefits gained from aggregation in ecological contexts where economic returns to scale make in-group cooperation and out-group exclusion worthwhile.
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